Issue with DOD 250

[Plaidesaurus]

I've built a number of pedals at this point and I'm a bit surprised to have an issue with such a simple pedal. I did box it and it works both clean and engaged but the engaged volume is weak, pretty much unity with the unengaged volume. The distortion acts like an old Tonebender: nada till you get to 9 and then it explodes with fuzz. My suspicion is with the 1N270 Diodes I bought from Newwark. They were cheap. They also came in a Schottky type casing, don't know if that makes a difference. But in the past I'd paid $2-3 each and they came in the glass bottle. I'm thinking one of the diodes looks blown.??? Any thoughts here?

 

[Erik S]

Is one of your electros in backwards?

 

[thomasbe86]

C7 is reversed, positive lug should be at the top.
Check the polarity of the diodes as well, D1 is backwards. Diodes should be fine, type is ok.

Check as well that you have contact between the third lug of the gain potentiometer, looks like a cold one :

 

[Erik S]

D1 is backwards.

I'm just a paint by the numbers guy, but both the square pads are on the same side, no?

 

[thomasbe86]

I'm just a paint by the numbers guy, but both the square pads are on the same side, no?

Oh that is definitely possible, I just compared to the board on the build docs, which seems a bit different (C4 and C5 arrangement for example)

 

[Erik S]

I just compared to the board on the build docs

Yup - I did the same thing at first, but it looks like the board has some changes since that doc.

 

[jimilee]

It’s always the simplest boards that don’t fire right up.

 

[Plaidesaurus]

It’s always the simplest boards that don’t fire right up.

Is one of your electros in backwards?

Replaced the filter cap with Proper orientation (fgs, what's wrong with me) and hit that solder point on the volume pot. Same situation though. When I get home this evening I'll look at voltages. Kind of a novice at this so I'm open to any other thoughts.

 

[Plaidesaurus]

It’s always the simplest boards that don’t fire right up.

So true, but good grief this shouldn't be that hard. I recently picked up and audio probe. No clue how to use it but will look on youtube.

It’s always the simplest boards that don’t fire right up.

Jimilee, I'm attaching a couple of pics of 1N270 diode readings. The clear glass diode is from a batch I used to build my last DOD 250. Sounded great as expected. Only had 1 left so I order some from Newark (one of those in the other pic attached). I have no solid reason to suspect these new diodes but... it's such a basic build these 1N270 diodes are the only different factor in the 2 builds. I don't know diddly about these 2 readings but thought I would see if you had any thoughts. Thanks for your time as always.

 

[Coda]

Got any other 741's to try?...

 

[Erik S]

Replaced the filter cap with Proper orientation

We’re stripes-down on both now, yeah?
And they’re the right values in the right spots?

 

[Nostradoomus]

I almost always use a C taper pot for drive here, linear just bunches it all up

 

[Plaidesaurus]

Pic 2

Got any other 741's to try?...

I do. Will swap out in the morning. Thx

 

[benny_profane]

I almost always use a C taper pot for drive here, linear just bunches it all up

Yeah that’d be my guess.

 

[Plaidesaurus]

I almost always use a C taper pot for drive here, linear just bunches it all up

Yeah that's a good call. I think it was one of the Tonebenders that call a B10k, maybe... I put a C1k in and it worked like a champ. I'm out of C1meg so I will add it to my next order. But any thoughts on a C500k as a replacement?

 

[Plaidesaurus]

So just following up again, should I give that C500k a shot since I don't have a C1M on hand? I hate to put that much heat on those pads if it doesn't work and I have to go with the C1M. But I just don't need to put in a parts order right now. I'd basically be paying shipping for that pot and a couple of other small things that can wait. Really appreciate all the input.

 

[Nostradoomus]

500k is the same as the 'grey spec" 250 and YJM too I think, it should do the trick

 

[Plaidesaurus]

Excellent! TY

 

[Plaidesaurus]

Put the C500K in place of gain knob and an A100k for the volume pot, That's the trick. Rocks pure old school. Thanks guys